Spark plug



Feb. 8, 1944. F. KAPP SPARK PLUG Filed April, 1,942

v 1NVENT0R.

FRED KAFP ATTDRAII@ FLL-5f Patented Feb. 8, 1944 UNITED STATES 2,340,963 SPARK PLUG Fred Kapp,

Application April 6,

1 Claim plugs of that type, whereby the higher explosive pressures are kept under safe control and prevented from breaking through and causing undue plug over-heating that results in the rapid destruction of the insulator tip and electrode, the said improved iirst seal consisting of a short small piece of soit metal tubing, such as copper or aluminum tubing, and in forming the insulator and central electrode in a. manner that will provide a space for receiving the soft metal tubing when the parts are assembled, and in also form# ing a shoulder on the central electrode and an inner seat in the insulator that will cause the soft metal tubing to imbed itself into andl completely cover all rough surfaces in the lower por--I tion of the insulator, not otherwise reachable, thus providing a positive gas-tight seal when the central electrode is tightly screwed into the insulator. p j y Another object of the present invention is to form a. series of circumferential grooves into and around the central .electrode above the threaded portion thereof and to also form angular or knurled roughened portions on t e c entral electrode between the grooves and apply asuitable spark plug sealing cement on the threaded portion of='the central electrode and into the grooves and roughened portions thereof, whereby the cement becomes absorbed around the threads and into and around the roughened portions, thereby forming a series of positive gas.. tight compression seals that will withstand the highest pressure and the severestuse.

, -An additional object ofthe present invention is to eliminate the conventional ange at the top portion of the central electrode and to provide a soft metal gasket, such as a copper gasket,l

. i and a threaded nut on the terminal post of the electrode, thus enabling a tight seal to be provided onto the top of the insulator without .in-

ter'fering with the proper sealing of the first seal .'50

'hereinbefore mentioned.'

An additional object of the present invention is to form the larger and upper -part of the centrai electrode out of a machined steel shaft and to weld an electrode nickel wire extension on the oakland, Calif. 1942, serial No. 437,773

lower end andto form a lap joint on said ends for enabling the parts to be properly Welded together.

A further additionalr object of the present invention is to provide a central electrode in a spark plug that is simple in construction and very economical to manufacture and wherein the life thereof is prolonged because of the improved structure and the unique combination and aI-, rangement of the parts employed.

Other objects and advantages of the invention will be apparent during the course of the following description. In the accompanying drawing forming a part of this specication and in which like numerals 'are employed to designate like parts throughout the same,

' Fig. 1` is a centralverticall longitudinal assembly view of a spark plug embodying my ingo'vention;

Fig. 2 is a side elevational view of my improved central electrode;

Fig. 3 is a horizontal sectional plan view taken on line 3-3 of Fig. 1, looking in the direction of 'the arrows, the sealing cement not being dise closed in order to better illustrate the outer roughened edge of the groove.

Fig. 4 is a perspective .view of an especially constructed soft metal tube that forms the nrst gas tight compression seal for my triple sealed.

central electrode;

Fig. 5 is a plan view of an especially constructed nut that is adapted to be threadedly secured onto the terminal post of the central electrode; and

Fig. 6 is a view in' elevation of my improved spark plug.

Referring in detail to the different parts, the numeral designates the outer metal casing preferably'forming a cylindrical shell having an enlarged hexagon upper end portion 9 and a reducedy externally threaded lower end portion lll that is adapted to be threadedly secured into the conventional spark plug threaded openings provided inthe cylinders of internal combustion en` gines. The insulating member I2 is preferably made of porcelain, but can be made of any`other suitable material and has an enlarged ycentral portion as shown in Fig. 1. Suitable gaskets I4 and ylli are provided at the upper and lower tapered ends of the enlarged portion and a gland nut iB is threadedly screwed into the Iupper internally threaded portion I1 of the casing 8 and 55. casing.

y serves to tightly hold thefinsulator I2 in said plished in the construction of spark plugs. l use of a copper or aluminum gasket 32 tightened The insulator has an enlarged bore I8, a reduced bore I8, an internally threaded portion and a, space 2i underneath v, the internally threaded' portion .forming ,a .tapered shoulder 22. 'Ihe improved centralelectrode, designated as a whole by the'numeral 23 is formed with a central threaded portion. 24= thatis adapted to applied sealing cement on the central electrode threads and the other roughened parts from l running down into the insulator ring tip, which engage in the internally threaded `portion 20 a of the insulator. The diameter ofthe lower extending portion ofthe central electrode is re-v duced as shown at forming a shoulder 2B directly at the bottom end of the threaded portion 24 as shown in Fig. 2.' y

As shown to advantage in Fig.v l anew and improved primary compression seal is produced by providing a piece of copper or aluminum tubing 21 onto the' electrode reduced extension 25 andagainsttheshoulder 26,' the lower tapered endof'said'tubing being tightly forced against -the tapered shoulder 22 of the insulator I2 whenv -the Ycentral electrode is screwed into the insulator. The soft copper or aluminum tubing as 22 and l26 will become imbedded into the surfaces Aof said shoulders and into the inner walls forming the space 2l in the insulator, producing an absolute gas-tight primary compressionseaL` The secondary seal is produced by providing a spark plug sealing cement around the threadedv portion 24' of the central electrode. The vthird compression seal is accomplishe'dby providing the central.- electrode, above said. threaded portion, witha series of circumferential grooves 28 and a 'series of roughened or knurled-portions 29 as shown in Fig. 2 and by applying sealing cement 30 -in said grooves and knurled portions as shown in Fig. 1. The terminal post oi the central electrode is threaded as indicated at 3| and a copper gasket 32 is mounted thereon andheld tightly sealed against the top of the insulator I2 by a hexagon nut 33. The numeral 34 designates the terminal cap to which the high tension current is delivered through a current conduct-f ing cable and connections not shown. The numeral 35 designates my V-type giounded'electrode that is fixed to the lower end portion I0 of the casing 3.

In constructing the central electrode' embodied in the present invention the upper part is made of a steel shaft machined to the' form illustrated and is 'providedwith a short electrode nickel wire 3S at the lower end portion asr shown in Figs. 1f

and 2. The connecting endsk of the lower central electrode portions '25 and 36 are formed'on a bias providing a lap joint as indicated at 31 and the two members are'substantially welded together. This construction n't only saves a large quantity of nickel but the lap joint makes a better Weld between the steel and the nickel wire. f

From the foregoing description taken in conjunction with the drawing'illustrating the present invention it will be particularly observed that certain definite improvements have been accom-- yThe providing of the copper'or aluminum tube il, and by interposing the same between the shoulder 22 and and 26 of the insulator and central electrode, respectively, 1 effect a positive gas-tight seal in a manner not heretofore accomplished in any spark plug and I also prevent the soi-t The.

Amust be free ,from v.the sealing cement to avoid tip breakage when in use.. The elimination of theflan'ge at the terminal end portion of the cen- -tral electrode and substitution of the gasket 32 and n ut 3 3 forsealing the top end of .the insulator l2 enables that end of. the insulator to be lo positively 'sealed without interfering with the proper sealing ofthe soft'metal tubing 21. Itis' accomplishes a three-fold result. Inorder to produce the most efficient spark it is necessary for. the central electrode to be made of a.. high .thus interposed between the opposing shoulders .electric conducting material -such as nickel.

However, in-order to' effect the most eiiicient seal with the copper or 'aluminum tubing 21 it isv necessary to make the central electrode oi a metal harderthan copper or aluminum, such. as steel. By thus constructing the major portion of the central electrode of machined steel and the inner end extension of nickel there is provided a most eiilcient seal with the soft metal tube. Furthermore, afmost efilcient spark is produced and at .the same time I decrease the amount of nickel A used, thus eect a saving inmaterial. Y

Attention is directed to the tubular member and the ways and means in which it can be used and shaped to accomplish a perfect gas tight metallic first compression seal around my particular formed spark plug center Wire, and in the threaded internal lower vshoulder center portion of my spark plug insulator, as herein referred to.

` My main object is to seal and keep sealed the insulator of my particular spark plug. The said tubular member 21 When properly assembled and tightenedinto my insulator will form a metallic compression seal in my previously patented triple sealed spark plug, Patent No. 2,226,414. It is to be noted that when my spark plug insulator is first molded, formed 0r casttoits proper size and shape, this tubular member having on its outside a roughened, grooved, barbed, distored or knurled surface as a means to anchor or imbed and to stay permanentlyl tight in the internal threaded lower shoulder center portion of my particular spark plug insulator, after the same is nished.

The sealing tubular member will also have a suitable inside thread. This thread may be straight or slightly cone shaped on both ends to receive any portion of a special iitted or threaded `portion of a spark plug central electrode, which shoulder center as a means for the proper sealcompression seal.

ing place, because Y`the lower insulator shoulder is thestrongest part and the insulator will withstand the greatest tightening pressure necessary to accomplish a metallic gas tight spark plug When the center electrode is'assembled as Li have described, it will'at all times make a solid contact with the insulator firing tip. Accordincly. the tremendous heat of the tip and the center electrode will be dissipated much faster.

It is a well known tact that compression leakage around a spark plug central electrode also increases the plugtemperature, creates an unbalanced -heat-range, expands the shell faster, loosens the insulator lower seat gasket, in some cases .burns the casket out entirely, and causes a waste in proper motor performance.

Having thus described my invention, I- claim: I

sion seal in the insulator. a sealing medium applied to the threaded portion-of the central electrode to form the second compression seal in the insulator, a series of circumferential grooves face of the central electrode being roughened. be-y formed into and around the central electrode beyond said threaded portion. thev peripheral sur- -v tween said grooves, a sealing medium provided insulator is sealed.

onto -said `roughened surface and into said grooves forming series of additionalcompression seais into the insulator, a gasket positioned on the outer end portion of the central electrode and against the outermost end of the insulator, and a nut threadedly secured onto the outer end portion of the central electrode and applied against the gasket thereon whereby the outer end of the FRED KAPP. 

